High accuracy expanded sector display and means and techniques for producing same



June 14, 1960 B. cuTLr-:R ETAL 2,941,199

HIGH ACCURACY EXPANDED SECTOR DISPLAY AND MEANS AND TECHNIQUES FOR PRODUCING SAME Filed Dec. 14, 1953 2 Sheets-Sheet 1 nux m A, .uuqw

f s nu 13 ,-f.

June 14, 1960 B. cuTLER ET AL 2,941,199 'HIGH ACCURACY EXPANDED SECTOR DISPLAY AND MEANS AND TECHNIQUES FOR PRODUCING SAME Filed Dec. 14, 1953 2 Sheets-Sheet 2 mean' 50am/v Carafe,

650265 5, Cen/v5,

JNVENToRs HIGH ACCURACY EXPANDED SECTOR DISPLAY ANNGD lSVIEANS AND TECHNIQUES FOR PRODUC- Filed Dec. 14, 1953, Ser. No. '397,842

8 Claims. (Cl. 343-11) The present invention relates to indicators useful in radar systems wherein it is desired to producean expanded display of a region scanned by a radiated beam so that resulting echo signals producing indications in such display may be more accurately studied and the position of targets causing such echo signals to be more accurately located.

Briefly, the present invention is described in conjunction with a conventional plan positionindicator system (P.P.I.) inwhich, as .is well known, an anenna is'rotated continuously through 360 and a corresponding 360 presentation or display is produced representing the area scanned by the beam. The conventional P.P.I. display is. produced by recurrent sweeps of the cathode ray beam recurrnetly sweeping out fromV the center ofthe display,` successive sweeps being displaced angularly a distance equal to the corresponding angular displacement of the antenna beam. The present invention allows effectively a sector of a P.P.I. display 4to be magnied to any desired degree and as shown herein such magnification or expansion is essentially an angular type of expansion with one degree angular displacement of the radiated beam corresponding to ten degrees in the display. Further, a particular section of the P.P.I. display may simultaneously be expanded in range using'a cathode ray tube with a diameter smaller than the diameter of the cathode ray .tube producing the conventional P.P.l. display. .In protively.

'Patented .lune y 1260 ice . 2 auxiliary tube is capable of producing an expanded representation of a selected portion of the P.P.I. display, such selected portion being entirely within" the'choice of an operator.

Another specic object of the-present invention 'to provide an indicating system of thischaract'er in which the center of the vexpanded presentation is indicated electronically on the face of the associated 4P.P.I.'fdispla'y".

The features of the present invention which'are be'- leved to be novel are set forth with particularity in Vthe appended claims. This invention itself, both toits organization and manner of operation, together with fur-I ther objects and advantages thereofgr'nayfbe bes't under# stood by reference to the following description taken in connection with the accompanying drawings' inwhich:

Figure 1 illustrates a vsystem embodying Afeatures'ofthe present invention.

Figure Z illustrates the expanded or magnified presentation or display produced using the system illustrated in Figure 1.

Figures 3 and 4 illustrate the positions the displays on the auxiliary cathode ray tube assume for the conditions when the center strobe of-the corresponding'PPl. display has an angular position of 270 and 135 'respee The system shown in Figure 1 includes a conventional rotating antenna 1,0 for producing a'beamll Aof radiated energy, such beam effectively being rotated through 360 with the area scanned by such beam in it'srnotiomibeing presented onthe face of the cathoderaytube 12 as a conventional P.P.I. display. vSuch P.P.I. 'display is represented generally in Figures 3 and 4.l In accordance ducing such expanded presenation or display, radial sweep i producing means are used but, in accordance with animportant feature of the present invention, the origin of such sweeps is eiectively displaced to a single point outside of the w'evwng surface of the cathode ray tube.

It is, therefore, a general object of the present invention to provide means and techniques for achieving the above indicated results.

A specific object of the present invention is to provide improved means and techniques whereby a selectedportion of a plan position indicator display may be magnified or expanded.

Another specic object of Ithe present invention is to provide improved means and techniques for obtaining an expanded display using simple and easily adjusted apparatus. Y

Another specic object of the present invention is to provide apparatus for obtaining an expanded presentation on the face of a cathode ray tube which is smaller in diameter than a related tube in a plan position indicator system. Another specific object of the present invention is to provide indicating apparatus of this character in which l two cathode ray tubes are used, one for providing a conventional P.P.I. display and the other. for producing an expanded represnetation of a portion ofv the P.P.I. display, so arranged that the portion of the display which is expanded is suitably indicated in the P.P.I. display.

Another specific object of the present invention is to provide an indicating system of this character in which a plan position indicator system `is associated withY an auxiliary cathode ray tube in such a manner that such with important features of the present invention apo'rtio'n of the area representedin the P.P.I. displayis magnified or expanded both angularly and in range and appears 'on the auxiliary cathode ray tube 14.

The deliection coil 38 of the tubev 12 is rotated in syny chronism with rotation of the antenna 10 so that angular displacements of the antenna beam 11 cause equal'angiilar displacements of the cathode beam sweeps 12A which define the P.P.I. display. The` dellection coil 42 of the tube 14 is also lrotated in synchronism with movement of the antenna 10 but at tenV times 'the speedso that a displacement of one degree of theantenna beam 11 corre-y sponds to a displacement of ten degrees of a sweep'deiin'- ing the display ontube 14. Further,- in accordance 'with play on tube 12'may beselected for expansion or magnitcation by an operator manually moving the mechani-r cally positioned cursor' 1,5 and by doing so' the orgin of the sweeps produced in tube 14is shifted as indicated in Figures'3 and 4, such Ashifting being obtained'due to automatic shifting of the oli-center coil 18 associated with tube 14. The display produced von tube 14' coniprises essentially seven visibly intensified radial lines (a portion only of which-are renderedvisible) each'repre-A senting an angular-distanceA of'one degree,'b'ut 'in fact being separated by ten degrees.` These radial lines are designated by the reference numerals 20, 21, 22, 23, 24, 25 and 26. The display on tube 14 includes also the series of' range marks 30, 31, 32, 33, 34, 35, 36, such range marks being displaced a distance'correspondng f to one hundred yards. Thecenter strobe 23 termed the thetal strobe is intensified more than the other strobes and is used to intensify the corresponding sweep 12A in the display shown in Figures 3 and 4. 'l Y' v Details of the system-shown'in Figure V1 for accomplishing these general purposesarenow described.

' to a one to one synchro transformer 46, while the output of .thesynchro 42 sapplied to the ten to one control transformer, 48 as well as to, theV control transformer 50. These control' transformers 46 and 48 each have their rotatable control elements Amechanically coupled to the shaft ofthe servo motor 55 driving the coil38. v The motor 55 is drivenby the output, ofthe servo power'amplier 58 which, in conventional manner, is coupled electrically to the control transformers 46 and 48V as well as ,toA an .alternating` current reference voltage source. The deflection coil 3S Vis coupled to the sweep generator 60 which is triggered periodically intimed relationship with pulses emitted from the antenna i-n accordance with triggers supplied from the system trigger generator 62. Y Y V The intensity of the cathode beam in the tube 12 'supplied with high voltage from the high voltage power supply 66, is, in general, intensified in the conventional manner in accordance with range mark puises developed in the range mark generator 70, and with echo signals supplied fromthesource-f/Z which is considered to be a conventional radar receiver associated inA conventional manner with the antenna 10.

Also, the cathode beam of tube `12, in accordance with one feature of the present invention,ris intensity modulated in timed relationship withV development of the center strobe 23 in Figure 2. Y

In order that these signals may cause visible 'indications at the proper time only, intensity gates 78 developed' in timed relationship with the sweeps are developed in the gate generator l80 and applied to a suitable intensity u control electrode of the tube 12.

The tube 12 has associatedjtherewith a cursor 15 which is a transparent element having an index line A thereon, such cursor being rotatably supported at a point on the central axis of the tube 12 and being rotatable manually being one slot or slit for each angle index mark 20, 21,

22, 23, 24, 25 and 26 which are produced using the slotted disk 92 in the manner described hereinafter. v

Radial sweeps are produced in the tube 14 in timed relationship with triggers from the generator 62, but

suchV sweeps are delayed'with respect to sweeps generated in tube 12, using delay means 94 which serves to delay the -triggers applied to the sweep gate generator 96 the desiredfamount. The output of the sweep gate generator V96 in the form of a gate 98 is applied to. the sweep gen- Vmarks developed in the range mark generator 108 represented by thecurved lines in Figure 2 as well as the azimuth index marks represented by the radial lines in Figure 2.k The range marks are delayed since the trigger which initiates Ythe production of such marks is delayed 25 by the aforementioned delay means 94.

The azimuth index marks are produced using the photoelectric cell 110 which is illuminated in accordance with the light prod-,uc'ed by the constantly energized lamp 112 transmitted recurrently through the slots or slits of the rotating disk 92, such disk 92 of course being `disposed mechanically between the source 112 and the photocell 110. The photocell 110 is serially `connected with the voltage source 115 Kand the load resistance 116 so asV to produce the voltage variation on the lead 118 represented lby the voltage variation 120, which comprises seven pulses, the center one of which represented by the reference numeral 122 is of appreciably larger intensity ythan the-other pulses. This relatively large pulse 122 'is producedV by the center slit 125 in the disk 92, such todifferent adjusted positions upon rotation of the knobY v ows may simply be a permanent magnet achieving the Y same magnetic result, namely, that of off centering theV sweeps produced in tube 14 to a point outside Vthe circumference ofthe tube 1f4`as indicated in Figure 2.

The deilection coil 42 of tube V14 is continuously rotated inV synchronism with movement of the antenna 10 but with an angular speed ten timesrthe angular speed of rotation of the beam 11 produced by the antenna 10. n

For increased accuracy, the coil 42 may be directly coupled mechanically to the antenna 10 through sui-table gearing but accurate results may likewise v`be obtained using a conventional servo follow up system as shownin Figure l. The coil 42 is driven by the servo drive motor y8 8'which receives energy from the servo amplifier 89 which is energized in conventional manner and this involves the application of Van' alternating current reference voltage to the amplifier l89 ,and an error'signal developed at the output of the Vcontrol transformer 50. The control transformer 50 hasits rotatable shaft yinterconnected thrugh suitable gearing to the shaft of Vthe drive motor 88. Such shaft 90 has also mounted thereon a disk V92 with seven radial slots or slits therein, there central slit being larger to allow the transmission of more light than the other slits. This voltage variation 120, the

. azimuth index signals are lapplied to an intensity control electrode Yof the tube This voltage variation on lead 118 is applied also `to the enabling gate multi-vibrator 125 Vwhich operates to initiate the start of the gate 127 in yaccord-ance lwith theV iirst pulse ofthe Vseries of pulses represented by the voltage variation 120;V and, the multivibrator stage 125 times its-elf out automatically ia short time after the last pulse in the series represented 4by the voltage 120 so as to form the enabling gate 127 which has a duration substantially equal to the time required for the production of the seven pulses `and such enabling gate 127 .of course appears contemporaneously with the production'of the voltage 120. ThisY enabling gate 127 is applied to,v the sweep gate generato-r 9.6 which is effective to produce the aforementioned intensity lgate 102,v Yand the sweep gate 98 only when theenabling gate 127 is present. ByV these means, sweeps are produced and rendered visible on the cathode ray tube 14 only within the limits defined bythe radial lines 20 and 26 in Figure 2. The centralpulse V122V of relatively large intensity causes the centralV strobe 23 in Figure 2 to be heavier than the otherstrobes. It. is desired to-produce a similar strobe on the P.P.I. indicator tube 12 eifected only byy such-center pulse.122,and for that purpose a conventional clipping or clipper stage has its input terminal connected to the lead 118; The clipping level of the stage 130V is Vindicatedbythe dottedrline 132 so that only one pulse, represented 'by the pulse 135 V'appears on the output'lead 1'36, such lead 136 ibeing coupled to an intensity control electroderof the tube 12.

In operation of the system shown in Figure 1, assuming that it is `desired vto magnify that portionsof the P.P.I.

s displayadjacent the 270 strobe vas indicated in Figure 3,

the cursor 15 is rotated by knob 15B to th'e 270 position and this automatically causes the o center coil 18, which is driven by the Selsyn system includingthe elements 84 and 86, to a position where the origin of the sweeps produced in tube 14 is shifted and the display indicated in Figure 3 is produced. A center strobe, i.e., the socalled thetal strobe produced electronically -in tube 12 and such strobe is coincident with the index line 15A painted or etched on the otherwise transparent cursor 15. Similarly, if it is desired to magnify that portion of the display adjacent the 135 position of tube 14, the cursor 1S is manually rotated to such 135 position and the results indicated in Figure 4 are obtained.

- For increased accuracy, the slotted disk 92 may be di- A rectly mechanically coupled to the antenna instead of through a servo mechanism as illustrated.

The tube 14 may be a so-called five-inch cathode ray tube with a four and one-half inch usable diameter and the off centering is such that the origin of the sweeps lies beyond the useful edge of the screen of the tube 14 while the system 4as described `allows a 6 angular sector in space to be expanded to cover a 60 angle on the face of the tube 14, other degrees of expansion may of course be obtained using ratios other than ten to one.

Figure 2 illustrates echo signals a, b and c from three isolated targets and it Iis observed that there is no spot size limitation associated with these .returning signals. The range or angle intervals from the reference point on the expanded display is either `added to or subtracted from the readings displayed on associated mechanical counters (for both azimuth and range) depending on the location of the target on the expanded display. Range is measured with respect t'o the leading edge of the target display whereas azimuth angle is measured with respect to the center of the target.

It is understood that while off centering to a degree wherein the origin of sweeps is outside the circumference of the viewing screen is used, the center of the sweeps may be so adjusted that it is likewise visible and this involves changing the amount of continuous current owing through the off center coil 18 or changing the strength of the permanent magnet in case ya permanent magnet is used for off centering purposes.

Furthermore, while it is preferred to use a photoelectrio cell in conjunction with a slotted disk as described above, it is conceivable that other means may be used to develop the vseries of pulses represented by the voltage 120 in timed relationship with movement of the scanning antenna.

While the particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

We claim:

1. In an arrangement of the character described, an antenna continuously rotating, a first cathode ray tube having first beam deflecting means synchronously rotated at the same angular speed as said antenna, a second cathode ray tube having second beam deflecting means synchronously rotated with said beam defiecting means but at an increased angular speed, manually operated cursor means operatively associated with said first cathode ray tube, Iand beam off-centering means associated with said second cathode ray tube and positioned in accordance with such cursor means.

2. indicating apparatus of the character described comprising, in combination, a first cathode ray tube having rst beam deflecting means associated therewith, a second cathode ray tube having second beam defiecting means associated therewith, means synchronously rotating said first and second beam deliecting means but with said second beam deliecting means rotating at a `higher yspeed than said first beam deecting means, manually operated cursor Vmeans associated with said first tube, cathode beam off-centering means associated with said second tube and positioned in accordance with movement of said cursor means.

` 3. Indicating apparatus comprising, in combination, a first cathode ray tube having first beam deecting means, a second cathode ray tube having second beam deliecting means, adjustable means Wherebythe center of sweeps produced by said second deecting means of said second tube is adjusted, means synchronously operating said lirst and second beam deiiecting means but with said Vsecond beam deflecting means moving the cathode beam of the second tube at a higher speed when the cathode beam of the first tube is moved by said first beam deflecting. means, indicating means associated with said first tube, means for moving said indicating means, and means operated automatically uponoperation of the last mentioned means for adjusting saidadjustable means to thereby alter the position of said center of sweeps.

4. indicating apparatus of the character described, the combination comprising, a first cathode tube having Vfirst beam deflecting means, a second cathode tube having second beam deecting means, means rotating said first and second beam defiecting means in synchronism but with said second beam deliecting means rotating at a speed higher than the speed of the first beam deflecting means, means associated with said first tube for positioning the central position of the cathode beam of a second tube from its off-center position, said second beam defiecting means being effective to produce sweeps of the cathode beam of the second tube from said offcenter position, means operated'synchronously with said second beam defiecting means for producing a series of pulses, means applying said series of pulses to an intensity control electrode of said second tube, and means applying at least one of said pulses to an intensity control electrode of said first tube.

5. In an arrangement of the character described, the combination comprising, a first cathode ray tube having first beam defiecting means, a second cathode ray tube having second beam deflecting means, means for rotating said first and second beam deflecting means in synchronism but with said second beam deflecting means rotating at a speed greater than said first beam deecting means, means operating synchronously with said second beam deiecting means for producing aseries of pulses, means applying said series of pulses to an intensity control electrode of said second tube, means applying at least one of said pulses to an intensity control electrode of said first tube, beam off-centering means associated with said second tube, land manually operated cursor means associated with said first tube, and means coupled between the cursor means and said beam off-centering means for positioning said beam olf-centering means in accordance with positioning of said cursor means.

6. In an indicating apparat-us of the character described, the combination comprising, a yiirst cathode ray tube having first beam defiecting means, a second cathode ray tube having second beam deecting means, means synchronously operating said iirst and second beam defiecting means but with said second beam deiiecting means operating at a higher speed than said rst beam defiecting means, means deriving a series of pulses recurrently lin and during movement of said second beam defiecting means, means for applying said series of pulses to an intensity control electrode of said second tube, and means applying only the center of said series of pulses to an intensity control electrode of said first tube.

7. An indicating apparatus of the character described, a cathode ray tube having beam deecting means, means deriving a series of pulses recurrently and in timed relationship with operation 0f said beam deliecting means, means applying said series of pulses to an intensity control electrode of said tube, and means for positioning the central positionof the cathode beam of said tube to a position off center of the center of the screen of said tube, said beam deecting means being ciective to sweep the cathode beam from said off-*center position, and means for rendering visible the indications produced by said cathode beam only during the time said series of pulses occur. f Y

, 8. In an arrangement of the character described, the combination comprising, a rsLcathode ray tube having first beam deecting means, a second cathode ray tube having a second beam deiiecting means, rst sweep generating means associated with said rst beam deecting means, second/'sweep generating means associated with said second beam deecting means, a source" of triggers,

means coupling said source to said IfirstV sweep generating means, delay means coupling said source to said second sweep Vgenerating means to delay the generation ofV the sweeps in said second tube with respectk to the generation of the sweeps in said rst tube, beaml ni-centering means associated with said second tube, cursor means associated with said rst tube, means interconnecting said cursor means and said beam off-centering means whereby said beam olf-centering means is positioned in accordance with positioning of said cursor means, means for developing a series of pulsesin accordance with operation of lsaid second beam -deecting means, means for applyingV said pulses to an intensity Vcontrol electroderof said second tube, and means for applying only one of said pulses to "an intensity control electrode of said first tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,422,697 MeachamV Y'June 24, 1947Y 2,585,868 Spaulding; 'Feb. l2, 1952 Y2,640,984 Sherwin .,June 2, Y1953 2,682,657 Haworth June 29, 1954 '2,754,508 

